NMR STRUCTURES OF FERREDOXIN CHLOROPLASTIC TRANSIT PEPTIDE FROM CHLAMYDOMONAS-REINHARDTII PROMOTED BY TRIFLUOROETHANOL IN AQUEOUS-SOLUTION

The 32-amino acid transit peptide of the unicellular green alga Chlamy domonas reinhardtii ferredoxin has been synthesized and analysed by NM R spectroscopy and circular dichroism. The results show that while the peptide is unstructured in water, it undergoes an alpha-helix formati on from residue 3 to 13 in a 30:70 molar-ratio mixture of 2,2,2-triflu oroethanol. The remainder of the peptide is still unstructured in CF3C D2OD/H2O mixtures, but is distributed on a side opposite to a hydropho bic ridge formed by Met(5), Phe(9) and Val(13) on the induced or-helix . The NMR structures driven by 2,2,2-trifluoroethanol in aqueous solut ion, are discussed in terms of potent interactions with the chloroplas t envelope and its translocation molecular machinery.